1. Field of the Invention
The invention relates to a bleah composition and a method utilizing the composition for bleaching surfaces.
2. The Prior Art
Dry bleaching powders, such as those for cleaning laundry, generally contain inorganic persalts as the active component. These persalts serve as sources of hydrogen peroxide. Normally, persalt bleach activity in aqueous solution is undetectable where temperatures are less than 100.degree. F. and delivery dosages less than 100 ppm active oxygen. The art has recognized, however, that bleaching under mild conditions may be effectuated through the use of activators.
Manganese (II) salts have been reported to be exceptionally effective in activating persalts under mild conditions. European Patent Application No. 0 082 563 discloses bleach compositions containing manganese (II) in conjunction with carbonate compounds. British Patent Application No. 82 36,005 describes manganese (II) in conjunction with a condensed phosphate/orthophosphate and an aluminosilicate, the builder combination enhancing bleach performance. European Patent Application No. 0 025 608 reveals peroxide activation catalysts consisting of zeolites or silicates whose cations have been exchanged for heavy metals such as manganese.
The aforementioned compositions still suffer from the presence of soluble manganese (II) ions. The soluble ions deposit on fabrics. Strong oxidants, such as hypochlorites, are frequently included in laundry washes. Deposited manganese will react with strong oxidants to form highly staining manganese dioxide.
U.S. Pat. No. 4,536,183 (Namnath) reports a system which overcomes the staining problem. The patent discloses a bleach activator comprising a water-soluble manganese (II) salt adsorbed onto a solid inorganic silicon support material prepared in such manner as not to contain free manganese (II) ions. Although this system provides adequate bleaching, more potent activators would be desirable where activator must be kept at a low level. Economics, peroxide stability, compatibility and environmental reasons encourage use of activator systems with the highest possible activity.
U.S. Pat. No. 4,208,295 (Sai et al.) discloses bleaching detergent compositions wherein water-insoluble aluminosilicates have had their cations partially exchanged with calcium or magnesium ions. Incorporation of calcium and magnesium was found to improve the storage stability of sodium percarbonate. Evidently, these particular divalent cations were not considered as bleach activators but, rather, as stabilizers to prevent decomposition of peroxide.
Consequently, it is an object of the present invention to provide a bleaching composition based on a supported manganese salt and a persalt that will not result in substrate staining.
A further object of this invention is to provide a bleach composition having exceptionally high activity.
Another object of this invention is to provide a method for improved bleaching of articles such as laundry.